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94 Renewable Energy Devices and Systems with Simulations in MATLAB and ANSYS ®
®

One year One day One hour
1.5 1.5 1.5
Solar irradiance, kW/m 2 1.0 Solar irradiance, kW/m 2 1.0 Solar irradiance, kW/m 2 1.0

0.5
0.5
0.5
0
Time, 1 month/div 0 Time, 4 h/div 0 Time, 10 min/div
One year One day One hour
40 40 40
Ambient temp., °C 20 0 Ambient temp., °C 20 0 Ambient temp., °C 20 0

–20 –20 –20
Time, 1 month/div Time, 4 h/div Time, 10 min/div

FIGURE 5.3 Examples of the variation of solar irradiance and ambient temperature during a year, a day, and
an hour, respectively.

the case of grid-connected PV inverters, the MPPT process may be executed only as long as the
PV-generated power is less than a predefined upper limit [5]. Else, the MPPT algorithm is deacti-
vated and the power produced by the PV source is regulated to remain at that limit. By controlling
the feed-in power to the electric grid, this control method enables to achieve a better utilization of
the electric grid and increase the utilization factor of the PV inverter, and simultaneously, the ther-
mal loading of its power semiconductors is reduced and their reliability is also increased.

MPPT methods

For uniform For nonuniform
solar irradiation solar irradiation

Constant voltage/ PV array
constant current reconfiguration
Perturbation and
observation Evolutionary
Incremental algorithms
conductance
Model based Numerical
Artificial algorithms
intelligence based
Single sensor Stochastic/chaos-
Numerical based algorithms
algorithms
Ripple correlation
control Distributed MPPT
Extremum seeking
control
Sliding-mode Other global
control MPPT methods

FIGURE 5.4 An overview of MPPT methods for PV arrays operating under uniform or nonuniform solar
irradiation conditions.